Process for producing a magnetized ring

ABSTRACT

Bearing or roller bearing with information sensor, of the type comprising a stationary element carrying at least one magnetic field sensor device and one rotating element carrying a multipole magnetized ring coaxial to the rotating element, which rotates in front of the sensor device and in which the ring is mounted in a support carried by the rotating element and is separated from the sensor device by an air gap, characterized in that the ring is provided with circumferentially distributed notches.

This is a division of application Ser. No. 292,852 filed 1/3/89 nowabandoned.

BACKGROUND OF THE INVENTION

The invention pertains to a bearing or roller bearing with aninformation sensor, of the type comprising a stationary element carryingat least one magnetic field sensor device and one rotating elementcarrying a multipole magnetized ring coaxial to said rotating element,which moves in front of the sensor device, and in which the ring ismounted in a nonmagnetic support carried by said rotating element and isseparated from the sensor device by an air gap. One such bearing hasbeen described in U.S. Pat. No. 4,732,494.

More specifically, the invention pertains to a process for producing themagnetized ring with good magnetization precision. Another object of theinvention is a sealed roller bearing with information sensor which makesuse of the magnetized ring.

SUMMARY OF THE INVENTION

The Applicants have observed that precise measurement of rotationalspeed, especially in installation application for speed-sensing bearingsor roller bearings in the automobile industry, requires that themagnetized ring be with successive poles at constant pitch with a highdegree of magnetization precision and a tolerance reduced to about 1%.

According to one aspect of the invention, the ring, previously securedon its rotating support is subjected to a dividing operation beforebeing penetrated by a flux of magnetic force produced by a magneticfield coaxial to the axis of rotation of the ring, the lines of force ofwhich are thus parallel.

The resulting invention thus furnishes the means necessary for achievingsufficient magnetization precision in the magnetized ring.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Other characteristics and advantages of the invention can be derivedfrom the description which follows, which refers to the attacheddrawings, in which:

FIG. 1 is a view of an axial cross section of the roller bearing;

FIGS. 2 and 3 are front views of two embodiments of the ring; and

FIG. 4 is a diagram of the sensor protection circuit.

DETAILED DESCRIPTION

According to FIG. 1, the ball bearing has a outer ring 10 and an innerring 11 capable of being either fixed or rotating, depending on themounting system used.

Rings 10 and 11 have raceways for rolling elements 12 in a cage 13,which retains them and provides angular positioning for them.

Outer ring 10, which is assumed to be fixed carries a radial lip seal 21in contact with inner ring 11 and a deflector 14, which defines a cavityin which a sensor 15 is located.

Another radial lip seal 22 is retained in a recess in deflector 14 andallows the connecting wires to the sensor to pass through.

Inner ring 11, which is assumed to be rotating has an installationsurface 16 for a support ring 17 of a magnetic or nonmagnetic material,immobilized against rotation by cementing, pressing, or any other means.

Ring 17 has a groove 18, the radial opening of which is separated fromsensor 15 in deflector 14 by an air gap e, the dimensions of which varydepending on the size of the bearing.

A magnetized ring 20 is housed in groove 18 As an example, ring 20 canbe made either of a treated metallic alloy or made from iron oxide and aplastic binder capable of being cast, machined, and radially magnetized.Ring 20 can, depending on the type of magnetization, be attacheddirectly to steel ring of the bearing and form, along with a carrierelement 17, a single part capable of producing magnetic fieldssufficient for stationary sensor 15.

With the aim of improving the magnetization quality of ring 20 (equalfield length and strength for each pole), ring 20 comprises notches 23,shown in FIG. 2 or segments produced by division into sections, as shownin FIG. 3. In this case, ring 20 is cut into sections after it has beencrimped or mounted in its support 17.

It is advantageous to create the notches or sections by the use of aprecision cutting machine, which can produce regular polarity withexcellent precision.

As an example, the circular polarization of the ring is produced, afterthe letter has been divided, by means of the magnetic flux produced by afield coaxial to the axis of rotation of the magnet by the use of themagnetoscopy technique. In this case, the notches or cuts generateleakage lines where the magnetic field is very intense over a shortdistance.

When the method of circular magnetization is used, the sectioned polesprovide a more intense field than the notched poles. It is possible toexploit this difference to create an imaginary reference mark at eachrevolution. If, on a ring notched at each pole, only one of the poles issectioned, an auxiliary sensor can be positioned so that it is sensitiveonly to the greater field intensity.

Under severe application conditions such as those encountered in theautomobile industry, sensor 15 is accompanied by a protection circuitespecially to protect against overvoltages and polarity reversals,and/or a two-wire connection as shown schematically in FIG. 4.

According to the diagram, a Zener diode 41 protects sensor 15 againstovervoltages at the + and - terminals of the circuit. A diode 40provides protection against polarity reversals at these same terminals.

A resistor 42 drops the voltage of the signal emitted by the sensor.

The circuit also makes available four distinct output voltage levels:

two levels, representing the low level ("0") and the high level ("1")during normal operation;

a zero supply voltage level in the event of a short circuit between theoutput conductors;

a maximum supply voltage level in the event of an interruption in one ofthe connections to resistor 42.

It is thus possible to monitor the operation of sensor 15.

The invention is by no means limited to the embodiment described andshown here by way of example In particular, the invention embracestechnical means equivalent to the means described or combinationsthereof to the extent that the latter are implemented in the spirit ofthe invention or carried out in the context of a measurement of speedinformation.

We claim:
 1. A process for producing a magnetized ring comprising thesteps of:cutting spaces in an annular ring whereby the annular ring isdivided into a plurality of segments; and magnetizing the annular ringwith a magnetic flux produced by a magnetic field coaxial to the centralaxis of the annular ring whereby the spaces provide areas of increasedmagnetic field intensity.
 2. The process as in claim 1, wherein theannular ring is mounted in a support ring prior to said cutting and saidspaces are completely through the annular ring separating the annularring segments.
 3. The process as in claim 1, wherein the spaces arepositioned around the annular ring dividing the annular ring into equallength segments.
 4. The process as in claim 1, wherein the magnetic fluxproduces multiple magnetic pole pairs, each magnetic pole paircoinciding with one of the annular ring segments, each pole of amagnetic pole pair is adjacent one of said spaces and each pole is ofthe opposite polarity of any adjacent poles.